Yu Cong
44db9807a1
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140 lines
3.6 KiB
HTML
140 lines
3.6 KiB
HTML
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="UTF-8">
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<title>Previous/Next example</title>
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</head>
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<body>
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<h1>'Previous/Next' example</h1>
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<div>
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<button id="prev" type="button">Previous</button>
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<button id="next" type="button">Next</button>
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<span>Page: <span id="page_num"></span> / <span id="page_count"></span></span>
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</div>
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<div>
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<canvas id="the-canvas" style="border: 1px solid black; direction: ltr;"></canvas>
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</div>
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<script src="../../node_modules/pdfjs-dist/build/pdf.mjs" type="module"></script>
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<script id="script" type="module">
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//
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// If absolute URL from the remote server is provided, configure the CORS
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// header on that server.
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//
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var url = '../../web/compressed.tracemonkey-pldi-09.pdf';
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//
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// In cases when the pdf.worker.js is located at the different folder than the
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// PDF.js's one, or the PDF.js is executed via eval(), the workerSrc property
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// shall be specified.
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//
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pdfjsLib.GlobalWorkerOptions.workerSrc =
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'../../node_modules/pdfjs-dist/build/pdf.worker.mjs';
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var pdfDoc = null,
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pageNum = 1,
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pageRendering = false,
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pageNumPending = null,
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scale = 0.8,
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canvas = document.getElementById('the-canvas'),
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ctx = canvas.getContext('2d');
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/**
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* Get page info from document, resize canvas accordingly, and render page.
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* @param num Page number.
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*/
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function renderPage(num) {
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pageRendering = true;
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// Using promise to fetch the page
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pdfDoc.getPage(num).then(function(page) {
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var viewport = page.getViewport({ scale: scale, });
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// Support HiDPI-screens.
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var outputScale = window.devicePixelRatio || 1;
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canvas.width = Math.floor(viewport.width * outputScale);
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canvas.height = Math.floor(viewport.height * outputScale);
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canvas.style.width = Math.floor(viewport.width) + "px";
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canvas.style.height = Math.floor(viewport.height) + "px";
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var transform = outputScale !== 1
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? [outputScale, 0, 0, outputScale, 0, 0]
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: null;
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// Render PDF page into canvas context
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var renderContext = {
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canvasContext: ctx,
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transform: transform,
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viewport: viewport,
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};
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var renderTask = page.render(renderContext);
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// Wait for rendering to finish
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renderTask.promise.then(function () {
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pageRendering = false;
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if (pageNumPending !== null) {
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// New page rendering is pending
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renderPage(pageNumPending);
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pageNumPending = null;
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}
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});
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});
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// Update page counters
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document.getElementById('page_num').textContent = num;
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}
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/**
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* If another page rendering in progress, waits until the rendering is
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* finished. Otherwise, executes rendering immediately.
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*/
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function queueRenderPage(num) {
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if (pageRendering) {
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pageNumPending = num;
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} else {
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renderPage(num);
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}
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}
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/**
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* Displays previous page.
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*/
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function onPrevPage() {
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if (pageNum <= 1) {
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return;
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}
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pageNum--;
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queueRenderPage(pageNum);
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}
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document.getElementById('prev').addEventListener('click', onPrevPage);
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/**
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* Displays next page.
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*/
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function onNextPage() {
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if (pageNum >= pdfDoc.numPages) {
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return;
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}
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pageNum++;
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queueRenderPage(pageNum);
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}
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document.getElementById('next').addEventListener('click', onNextPage);
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/**
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* Asynchronously downloads PDF.
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*/
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var loadingTask = pdfjsLib.getDocument(url);
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pdfDoc = await loadingTask.promise;
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document.getElementById('page_count').textContent = pdfDoc.numPages;
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// Initial/first page rendering
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renderPage(pageNum);
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</script>
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</body>
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</html>
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